This study is examining the natural course of age-related changes in muscular strength to determines the relationship of age and strength levels to body composition and health status. The relationship of age to maximal force production (strength) of the upper and lower body musculature during the concentric (shortening) and eccentric (elongation) phases of movement are presently being established. In addition, strength measures are being assessed at slow, fast and zero (isometric) speeds to determine if there is a preferential loss of force at fast speeds with age. Analyses of changes in force production in the prime mover is being compared to changes in the antagonist muscle group to determine if muscle balance is affected with age. In addition, the angle of greatest force production is being assessed to determine if this angle changes with age. Almost 400 male and female subjects from the 20s through the 80s have been tested since implementation. Age associated declines are found in cross-sectional analysis for both concentric and eccentric testing for all muscle groups and speeds. The rate of decline is greater in the quadriceps femoris than for the biceps brachii. The rates of decline in concentric and eccentric strength tend to be parallel. LSB has proposed a long term initiative, "BLSA Initiative on Age-associated Changes in Functional Ability (Frailty)." The initiative consists of three projects: 1) to develop a quantitative functional assessment for the BLSA; 2) to investigate how changing vision effects performance; and, 3) a protocol is currently being developed to estimate the role of age associated changes in the peripheral nerve on the age associated changes in muscle strength. We plan to estimate the number of functional motor units and to follow longitudinal changes in strength and unit count.